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RSS2010 Vol. 22, No. 02
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2010,
22.
Abstract:
A crystal electro-optical switch which can substitute the image intensifier’s shutter was designed using the electro-optical effect of crystal. The principle of the electro-optical effect and the necessity and feasibility of the electro-optical switch was illustrated. Optical path system of the switch and the spot figure of switch on/off were obtained by using the optics software Zemax. The results of simulation and experiment illustrate that the crystal electro-optical switch can be used in the system of lidar with exposure time of nanosecond level.
A crystal electro-optical switch which can substitute the image intensifier’s shutter was designed using the electro-optical effect of crystal. The principle of the electro-optical effect and the necessity and feasibility of the electro-optical switch was illustrated. Optical path system of the switch and the spot figure of switch on/off were obtained by using the optics software Zemax. The results of simulation and experiment illustrate that the crystal electro-optical switch can be used in the system of lidar with exposure time of nanosecond level.
2010,
22.
Abstract:
A highly efficient high-repetition-rate CW laser diode end-pumped acousto-optically (AO) Q-switched eye-safe intracavity optical parametric oscillator at 1.53 μm was experimentally investigated. The 20 mm long KTA crystal cut for typeⅡ noncritical phase matching was adopted as the nonlinear crystal parametric converter in this experiment. We have achieved the signal average power of 2.6 W under the LD pumping power of 13.7 W and the pulse repetition rate of 60 kHz, corresponding to an optical-to-optical conversion efficiency of 19%. At the highest output power of 2.6 W, the signal pulse duration of 2.9 ns was obtained, corresponding to the single pulse energy of 43.3 μJ and peak power of 15 kW, respectively.
A highly efficient high-repetition-rate CW laser diode end-pumped acousto-optically (AO) Q-switched eye-safe intracavity optical parametric oscillator at 1.53 μm was experimentally investigated. The 20 mm long KTA crystal cut for typeⅡ noncritical phase matching was adopted as the nonlinear crystal parametric converter in this experiment. We have achieved the signal average power of 2.6 W under the LD pumping power of 13.7 W and the pulse repetition rate of 60 kHz, corresponding to an optical-to-optical conversion efficiency of 19%. At the highest output power of 2.6 W, the signal pulse duration of 2.9 ns was obtained, corresponding to the single pulse energy of 43.3 μJ and peak power of 15 kW, respectively.
2010,
22.
Abstract:
The charge measurement process of CCD in normal work state has been analyzed. It is indicated that the mode of charge injecting to the measurement capacitor is the periodic narrow pulse that has a low fill factor when the CCD is normal. After the charge signal is measured, the feed-through level is restored under the effective resetting action.According to the condition under which the excessive saturation state of CCD happens and potential characteristics in the signal charge transfer channel of CCD,we put forward the physical mechanism of the CCD excessive saturation effect. That is, an optoelectronic current source is formed by laser in the irridiated spot of the CCD. The charge generated by laser crams the potential well of the CCD and then makes the CCD become a current device from a
The charge measurement process of CCD in normal work state has been analyzed. It is indicated that the mode of charge injecting to the measurement capacitor is the periodic narrow pulse that has a low fill factor when the CCD is normal. After the charge signal is measured, the feed-through level is restored under the effective resetting action.According to the condition under which the excessive saturation state of CCD happens and potential characteristics in the signal charge transfer channel of CCD,we put forward the physical mechanism of the CCD excessive saturation effect. That is, an optoelectronic current source is formed by laser in the irridiated spot of the CCD. The charge generated by laser crams the potential well of the CCD and then makes the CCD become a current device from a
2010,
22.
Abstract:
The paper demonstrates a nonlinear design of the stabilization system of Fabry-Perot(F-P) interferometer which is a frequency discriminator used in double-edge wind lidar. First, a nonlinear model is set up to describe the F-P interferometer transmission peak locking problem. The disturbance caused by air pressure fluctuation, temperature change or mechanical vibration is characterized by the unknown external force acting on piezoelectric ceramics. For such a disturbance rejection problem, the nonlinear proportional-integral-derivative(PID) control is developed by utilizing arctan function to improve the feedback gain of the typical PID control design. The results show that, with the new controller, the discriminator can be stabilized much faster, and the steady-state error is approximatel
The paper demonstrates a nonlinear design of the stabilization system of Fabry-Perot(F-P) interferometer which is a frequency discriminator used in double-edge wind lidar. First, a nonlinear model is set up to describe the F-P interferometer transmission peak locking problem. The disturbance caused by air pressure fluctuation, temperature change or mechanical vibration is characterized by the unknown external force acting on piezoelectric ceramics. For such a disturbance rejection problem, the nonlinear proportional-integral-derivative(PID) control is developed by utilizing arctan function to improve the feedback gain of the typical PID control design. The results show that, with the new controller, the discriminator can be stabilized much faster, and the steady-state error is approximatel
2010,
22.
Abstract:
In two-deformablemirror adaptive optics systems, the outing main laser compared to the beacon light should have the same amplitude distribution and conjugated phase, and when the main laser reaches the target with the same distribution as the beacon light from the target, the main laser’s amplitude and phase have been corrected. According to the two-deformable-mirror adaptive optics technology, this paper presents a method based on adaptive optics system to control the nearfield intensity of laser beam, and experimentally validates the feasibility of the two-deformable-mirror technology. This method uses the Hartmann-Shack(H-S) wave-front sensor to detect the wave-front information, which is utilized in the control of the deformable mirror to achieve near-field intensity control over
In two-deformablemirror adaptive optics systems, the outing main laser compared to the beacon light should have the same amplitude distribution and conjugated phase, and when the main laser reaches the target with the same distribution as the beacon light from the target, the main laser’s amplitude and phase have been corrected. According to the two-deformable-mirror adaptive optics technology, this paper presents a method based on adaptive optics system to control the nearfield intensity of laser beam, and experimentally validates the feasibility of the two-deformable-mirror technology. This method uses the Hartmann-Shack(H-S) wave-front sensor to detect the wave-front information, which is utilized in the control of the deformable mirror to achieve near-field intensity control over
2010,
22.
Abstract:
Experimental results of spectral beam combining for two fiber lasers in an external cavity have been reported,which used largemode-area Er3+/Yb3+ co-doped doublecladding fiber as the gain medium. The maximal output power of 0.80 W with combining efficiency more than 82.5% was obtained. The effect of changing fiber-end distance from the system axis, as well as rotation of the grating on spectral output and combining efficiency was demonstrated and analyzed, which shows that one of the spectra is multimoded when the distance of fiber end from the system axis is beyond a certain range, and combining efficiency increases when the angle of the grating decreases with respect to horizontal plane．
Experimental results of spectral beam combining for two fiber lasers in an external cavity have been reported,which used largemode-area Er3+/Yb3+ co-doped doublecladding fiber as the gain medium. The maximal output power of 0.80 W with combining efficiency more than 82.5% was obtained. The effect of changing fiber-end distance from the system axis, as well as rotation of the grating on spectral output and combining efficiency was demonstrated and analyzed, which shows that one of the spectra is multimoded when the distance of fiber end from the system axis is beyond a certain range, and combining efficiency increases when the angle of the grating decreases with respect to horizontal plane．
2010,
22.
Abstract:
Thermal blooming anisoplanatic effect of the circular-symmetric flattened beam is analysed by the method of Gaussian beam expansion. Wave-front distortion of the thermal blooming anisoplanatic effect is expanded by the Zernike polynomials, and the Zernike coefficient and fitting error are obtained. The corrected error of the thermal blooming calculated by the numerical method is consistent with the outcome of the theoretical formula. The numerical simulation results also indicate that the angular anisoplanatic error varies proportionally to the square of the anisoplanatic angle, and the focus anisoplanatic error is in inverse proportion to the 1.71th power of the beacon height, if the caliber size is invariable.
Thermal blooming anisoplanatic effect of the circular-symmetric flattened beam is analysed by the method of Gaussian beam expansion. Wave-front distortion of the thermal blooming anisoplanatic effect is expanded by the Zernike polynomials, and the Zernike coefficient and fitting error are obtained. The corrected error of the thermal blooming calculated by the numerical method is consistent with the outcome of the theoretical formula. The numerical simulation results also indicate that the angular anisoplanatic error varies proportionally to the square of the anisoplanatic angle, and the focus anisoplanatic error is in inverse proportion to the 1.71th power of the beacon height, if the caliber size is invariable.
2010,
22.
Abstract:
By expanding the LP01 mode into a linear superposition of Laguerre-Gaussian modes and using Collins formula, the analytical propagation equation of wave-guide modes in a single-mode fiber through paraxial ABCD optical systems is derived. The free-space propagation and focusing properties of the LP01 mode are studied and compared with those of the fundamental Gaussian mode. It is shown that the Gaussian mode in place of the LP01 mode may introduce some errors. In the focused field of the LP01 mode there exists the focal shift which increases with decreasing Fresnel number. By a suitable choice of the Fresnel number, a long focusing depth may appear for the LP01 mode which is quite different from that of the focused Gaussian mode.
By expanding the LP01 mode into a linear superposition of Laguerre-Gaussian modes and using Collins formula, the analytical propagation equation of wave-guide modes in a single-mode fiber through paraxial ABCD optical systems is derived. The free-space propagation and focusing properties of the LP01 mode are studied and compared with those of the fundamental Gaussian mode. It is shown that the Gaussian mode in place of the LP01 mode may introduce some errors. In the focused field of the LP01 mode there exists the focal shift which increases with decreasing Fresnel number. By a suitable choice of the Fresnel number, a long focusing depth may appear for the LP01 mode which is quite different from that of the focused Gaussian mode.
2010,
22.
Abstract:
Based on the Frantz-Nodvik physical model, the energy fluence of backward-reflected laser in a high power laser amplifier has been investigated by solving the rate equations in consideration of relaxation between lower and upper laser states. The laser chain is composed of Nd-doped phosphate glass amplifiers that can provide 2.50 kJ with the pulse duration of 1.0 ns. Due to the considerable difference of remaining gain in laser amplifiers, the energy fluence is significantly different. Compared with that utilizing one amplifier with the diameter of 70 mm，the laser chain including two may take a bigger risk of being destroyed.
Based on the Frantz-Nodvik physical model, the energy fluence of backward-reflected laser in a high power laser amplifier has been investigated by solving the rate equations in consideration of relaxation between lower and upper laser states. The laser chain is composed of Nd-doped phosphate glass amplifiers that can provide 2.50 kJ with the pulse duration of 1.0 ns. Due to the considerable difference of remaining gain in laser amplifiers, the energy fluence is significantly different. Compared with that utilizing one amplifier with the diameter of 70 mm，the laser chain including two may take a bigger risk of being destroyed.
2010,
22.
Abstract:
A novel method, two-step stimulated Brillouin scattering(SBS) structure, was put forward to controlling modulation and improving pulse shape quality in the SBS pulse compression system. And this method, which uses two compression stages to extract sub-peaks’ energy to the peak, is likely to be a new approach to obtain pulses with short duration and high shape quality. The performance of the two-step SBS pulse compression system were investigated theoretically and experimentally. The experiment investigation was conducted using CCl4 and FC-72 as the SBS media. High-quality pulse shapes with no modulation were obtained, which agrees well with the simulation results.
A novel method, two-step stimulated Brillouin scattering(SBS) structure, was put forward to controlling modulation and improving pulse shape quality in the SBS pulse compression system. And this method, which uses two compression stages to extract sub-peaks’ energy to the peak, is likely to be a new approach to obtain pulses with short duration and high shape quality. The performance of the two-step SBS pulse compression system were investigated theoretically and experimentally. The experiment investigation was conducted using CCl4 and FC-72 as the SBS media. High-quality pulse shapes with no modulation were obtained, which agrees well with the simulation results.
2010,
22.
Abstract:
Four different power samples, sulfanilic acid anhydrous, soluble starch, graphite and calcium carbonate,with different content of carbon were used to determine the influence of element speciation on the properties of laser-induced spectroscopy. The srectral line of CI 247.856 nm was chosen to analye the excitation properties of laser-induced plasma of different carbon speciations. The chemical compositions, molecular binding forces of materials on were used to account for the differences of spectral properties among different forms of carbons. The results show that the excitation energy of carbon in compound with complex structure and greater chemical bond energy requires relatively more energy.
Four different power samples, sulfanilic acid anhydrous, soluble starch, graphite and calcium carbonate,with different content of carbon were used to determine the influence of element speciation on the properties of laser-induced spectroscopy. The srectral line of CI 247.856 nm was chosen to analye the excitation properties of laser-induced plasma of different carbon speciations. The chemical compositions, molecular binding forces of materials on were used to account for the differences of spectral properties among different forms of carbons. The results show that the excitation energy of carbon in compound with complex structure and greater chemical bond energy requires relatively more energy.
2010,
22.
Abstract:
This paper reports the experimental investigation on the principle of axisymmetric-fold combination CO2 laser. The laser operated successfully in CW mode. The optimum gas mixture ratio and the gas pressure of the laser were determined. Different aspects of the CO2 laser were studied including the variations of excitation threshold voltage and output power with discharge current. The output spots and the light intensity distribution of the laser beam were obtained. The convergence of the laser beam was performed through an optical imaging system. The laser was successfully constructed, operated and tested for different applications within the limits of its maximum output power of 58 W.
This paper reports the experimental investigation on the principle of axisymmetric-fold combination CO2 laser. The laser operated successfully in CW mode. The optimum gas mixture ratio and the gas pressure of the laser were determined. Different aspects of the CO2 laser were studied including the variations of excitation threshold voltage and output power with discharge current. The output spots and the light intensity distribution of the laser beam were obtained. The convergence of the laser beam was performed through an optical imaging system. The laser was successfully constructed, operated and tested for different applications within the limits of its maximum output power of 58 W.
2010,
22.
Abstract:
The preparation of the tungsten foil for equation of state(EOS) target was studied by electropolishing in sulfuric acid-methanol. The anodic polarization curve of the tungsten foil was analyzed, and the surface topography, grain orientation, density and thickness uniformity were tested. The tungsten foil was prepared with high surface quality (RMS roughness less than 50 nm) and thickness uniformity beyond 99%, and could keep the density of raw materials. This foil could satisfy the requirement of laser driven materials for the research of high temperature and pressure EOS. Thus electropolishing is a significant method for preparating the foil which can fulfill the requirement of EOS target.
The preparation of the tungsten foil for equation of state(EOS) target was studied by electropolishing in sulfuric acid-methanol. The anodic polarization curve of the tungsten foil was analyzed, and the surface topography, grain orientation, density and thickness uniformity were tested. The tungsten foil was prepared with high surface quality (RMS roughness less than 50 nm) and thickness uniformity beyond 99%, and could keep the density of raw materials. This foil could satisfy the requirement of laser driven materials for the research of high temperature and pressure EOS. Thus electropolishing is a significant method for preparating the foil which can fulfill the requirement of EOS target.
2010,
22.
Abstract:
The density non-uniformity exsiting in most low-density foams will affect performance of the foams. The trimethylolpropane trimethacrylate(TMPTA) foam targets were prepared and controlling methods of the foams, density uniformity were explored together with its forming mechanism. It has been found that the UV-light with high intensity can improve the distribution uniformity of the free radicals induced by UV photons in the solvents, thus improve the density uniformity of the foams. In addition, container wall would influence the concentration distribution of the solution, which affects the density uniformity of the foams. Thus, the UV-light with high intensity was chosen together with polytetrafluoroethylene molds instead of glass molds to prepare the foams with the density non-uniformity
The density non-uniformity exsiting in most low-density foams will affect performance of the foams. The trimethylolpropane trimethacrylate(TMPTA) foam targets were prepared and controlling methods of the foams, density uniformity were explored together with its forming mechanism. It has been found that the UV-light with high intensity can improve the distribution uniformity of the free radicals induced by UV photons in the solvents, thus improve the density uniformity of the foams. In addition, container wall would influence the concentration distribution of the solution, which affects the density uniformity of the foams. Thus, the UV-light with high intensity was chosen together with polytetrafluoroethylene molds instead of glass molds to prepare the foams with the density non-uniformity
2010,
22.
Abstract:
A low-cost and high-stability microwave plasma torch source based on BJ22 rectangular waveguide was developed, which is supplied by the (2.45±0.05) GHz frequency microwave source. The entire system consists of a 1~10 kW magnetron power supply, a circulator, a tuning section and a waveguide resonator. Atmospheric open microwave plasma was produced by the interaction of the work gas and the high electrical field, which was generated between the gas nozzle and the waveguide aperture by specific tuning structure. Several key factors were simulated to get the effect of key factors on electric field strength and then the microwave resonator was designed. A variety of gases were used to produce the plasma including argon, helium, nitrogen and air. In this paper, the basic characteristics of the
A low-cost and high-stability microwave plasma torch source based on BJ22 rectangular waveguide was developed, which is supplied by the (2.45±0.05) GHz frequency microwave source. The entire system consists of a 1~10 kW magnetron power supply, a circulator, a tuning section and a waveguide resonator. Atmospheric open microwave plasma was produced by the interaction of the work gas and the high electrical field, which was generated between the gas nozzle and the waveguide aperture by specific tuning structure. Several key factors were simulated to get the effect of key factors on electric field strength and then the microwave resonator was designed. A variety of gases were used to produce the plasma including argon, helium, nitrogen and air. In this paper, the basic characteristics of the
2010,
22.
Abstract:
Mast aspheric optical elements fabricated using computer controlled optical surfacing (CCOS) technology have midfrequency errors on their surfaces. These errors come about because of the small tools removal characteristic and the misfit between rigid tools and aspheric surface. A passive semi-rigid tool, which can smooth ripple errors efficiently, is introduced in this paper. The tool is composed of a rigid layer, a compliant layer and a polishing layer. The passive tool works like a high-pass filter, smoothing the ripple out without damaging the surface figure. The expression of polishing pressure under the lap is deduced based on elastic plate theory. The relationship between the basic parameters of the lap and error frequency is also discussed. To testify the smoothing ability of the
Mast aspheric optical elements fabricated using computer controlled optical surfacing (CCOS) technology have midfrequency errors on their surfaces. These errors come about because of the small tools removal characteristic and the misfit between rigid tools and aspheric surface. A passive semi-rigid tool, which can smooth ripple errors efficiently, is introduced in this paper. The tool is composed of a rigid layer, a compliant layer and a polishing layer. The passive tool works like a high-pass filter, smoothing the ripple out without damaging the surface figure. The expression of polishing pressure under the lap is deduced based on elastic plate theory. The relationship between the basic parameters of the lap and error frequency is also discussed. To testify the smoothing ability of the
2010,
22.
Abstract:
DKDP crystal was grown from 80%-deuterated solution of high pure materials and the crystal was cut to type Ⅱ tripler sample. The major problem of DKDP crystal for third harmonic generation (THG) is its low laser-induced damage thres-hold with respect to KDP, which greatly limits energy fluence of output laser and crystals’ life. Laser-induced damage thres-hold of DKDP crystal for THG was measured under different wavelengths and the effect of laser annealing was also investigated. The experiment shows that laser annealing could obviously improve laser-induced damage threshold of DKDP crystal. The thres-hold is improved to 1.4, 1.9 or 2.7 times that before annealing for fundamental, second or third harmonic, respectively. Thus laser annealing is an effective approach to enhance laser-induc
DKDP crystal was grown from 80%-deuterated solution of high pure materials and the crystal was cut to type Ⅱ tripler sample. The major problem of DKDP crystal for third harmonic generation (THG) is its low laser-induced damage thres-hold with respect to KDP, which greatly limits energy fluence of output laser and crystals’ life. Laser-induced damage thres-hold of DKDP crystal for THG was measured under different wavelengths and the effect of laser annealing was also investigated. The experiment shows that laser annealing could obviously improve laser-induced damage threshold of DKDP crystal. The thres-hold is improved to 1.4, 1.9 or 2.7 times that before annealing for fundamental, second or third harmonic, respectively. Thus laser annealing is an effective approach to enhance laser-induc
2010,
22.
Abstract:
Growth method is the dominating factor which greatly influences the growth and the laser damage threshold of the DKDP single crystal. In this paper, DKDP crystals were grown from 85%-deuterated solution by using traditional temperature-reduction method and point-seed rapid growth method respectively. Optical transmission and laser damage in unconditioned type Ⅱ tripler-cut DKDP crystals have been studied. It is found that, due to super-saturation effect, by using point-seed rapid growth method, the growth rate of DKDP is about 15 mm/day, which is ten times that by using traditional growth method. But more metallic ionic impurities and inclusions lead to the deterioration in the transmission spectra and laser induced damage threshold.
Growth method is the dominating factor which greatly influences the growth and the laser damage threshold of the DKDP single crystal. In this paper, DKDP crystals were grown from 85%-deuterated solution by using traditional temperature-reduction method and point-seed rapid growth method respectively. Optical transmission and laser damage in unconditioned type Ⅱ tripler-cut DKDP crystals have been studied. It is found that, due to super-saturation effect, by using point-seed rapid growth method, the growth rate of DKDP is about 15 mm/day, which is ten times that by using traditional growth method. But more metallic ionic impurities and inclusions lead to the deterioration in the transmission spectra and laser induced damage threshold.
2010,
22.
Abstract:
The single-layer SiO2, single-layer ZrO2, ZrO2/SiO2/ZrO2 three-layer thin films were deposited on K9 glass by sol-gel spin-coating method. The colloidal suspension of ZrO2 was prepared by Zr(OPr)4 and that of SiO2 was prepared by TEOS. An ellipsometer was used to measure the thickness and refractive index of the films, and a UV-Vis spectrophotometer was used to measure the transmittance of the films. By the TFCalc thin film design software, the transmittance of the films was simulated. The vertical section of the ZrO2/SiO2/ZrO2 three-layer film was probed by scanning electron microscopy, X-ray photoelectron spectroscopy(XPS) was used to measure the variation of compositi
The single-layer SiO2, single-layer ZrO2, ZrO2/SiO2/ZrO2 three-layer thin films were deposited on K9 glass by sol-gel spin-coating method. The colloidal suspension of ZrO2 was prepared by Zr(OPr)4 and that of SiO2 was prepared by TEOS. An ellipsometer was used to measure the thickness and refractive index of the films, and a UV-Vis spectrophotometer was used to measure the transmittance of the films. By the TFCalc thin film design software, the transmittance of the films was simulated. The vertical section of the ZrO2/SiO2/ZrO2 three-layer film was probed by scanning electron microscopy, X-ray photoelectron spectroscopy(XPS) was used to measure the variation of compositi
2010,
22.
Abstract:
Based on the elasticity mechanics theory, the principle and calculation method of stressed mirror polishing(SMP) are studied, as well as the simulation of complex surfaces with elastic optical thin plates. The change of sphere into axisymmetric aspheric surface is analyzed with forces applied around the spherical mirror. Considering the fabrication of a parabolic mirror, the deformation and the maximal stress of thin mirror plate have been simulated with bending moments applied around. The simulated deformation between spheree and paraboloid is compared with the theoretical deformation, which indicates that SMP sphere and paraboloid is compared with the theoretical deformation, which indicates that SMP can produce rotationally symmetric aspheric mirrors with high precision and efficiency.
Based on the elasticity mechanics theory, the principle and calculation method of stressed mirror polishing(SMP) are studied, as well as the simulation of complex surfaces with elastic optical thin plates. The change of sphere into axisymmetric aspheric surface is analyzed with forces applied around the spherical mirror. Considering the fabrication of a parabolic mirror, the deformation and the maximal stress of thin mirror plate have been simulated with bending moments applied around. The simulated deformation between spheree and paraboloid is compared with the theoretical deformation, which indicates that SMP sphere and paraboloid is compared with the theoretical deformation, which indicates that SMP can produce rotationally symmetric aspheric mirrors with high precision and efficiency.
2010,
22.
Abstract:
By solving a thermal conduction equation with Green’s function method, a theoretical model is developed to describe the three-dimensional temperature distribution of a highly reflective optical coating sample with a finite radial size irradiated by a continuous-wave laser beam. The radial boundary conditions and heat losses from the sample to the environment are both considered in this model. To verify the theoretical model, temperature distributions are numerically calculated under different pump-beam profiles and beam radii and the results are in good agreement with those of the finite-element method. Furthermore, the influence of different thermal loss coefficients on the temperature distributions of the sample irradiated by laser beams is discussed.
By solving a thermal conduction equation with Green’s function method, a theoretical model is developed to describe the three-dimensional temperature distribution of a highly reflective optical coating sample with a finite radial size irradiated by a continuous-wave laser beam. The radial boundary conditions and heat losses from the sample to the environment are both considered in this model. To verify the theoretical model, temperature distributions are numerically calculated under different pump-beam profiles and beam radii and the results are in good agreement with those of the finite-element method. Furthermore, the influence of different thermal loss coefficients on the temperature distributions of the sample irradiated by laser beams is discussed.
2010,
22.
Abstract:
Based on the detailed configurations model, a one-dimensional non-equilibrium magnetohydrodynamics modeling has been developed to study the physical process of aluminum wire array Z-pinch implosion and non-equilibrium radiation. The code solves the transfer of line radiation by using escape probability approximation, and solves the transfer of continuum by using multi-group diffusion approximation. It is shown that the calculated peak power, FWHM(full width at half magnitude) and total energy of the radiation pulse accord well with the experimental results besides the agreement of the dynamics of Z-pinch implosion. The energy spectrum of the total radiation has been discussed, which shows the substantial importance of non-equilibrium radiation in Z-pinch implosion. The role of three channe
Based on the detailed configurations model, a one-dimensional non-equilibrium magnetohydrodynamics modeling has been developed to study the physical process of aluminum wire array Z-pinch implosion and non-equilibrium radiation. The code solves the transfer of line radiation by using escape probability approximation, and solves the transfer of continuum by using multi-group diffusion approximation. It is shown that the calculated peak power, FWHM(full width at half magnitude) and total energy of the radiation pulse accord well with the experimental results besides the agreement of the dynamics of Z-pinch implosion. The energy spectrum of the total radiation has been discussed, which shows the substantial importance of non-equilibrium radiation in Z-pinch implosion. The role of three channe
2010,
22.
Abstract:
Based on surface arc plasma aerodynamic actuation, demonstration experiments have been conducted on the variation rules of the shock wave’s position, degree and intensity through varying actuation conditions (such as discharge channel number and spacing, DC discharge voltage, ramp angle and magnetic field) in Mach number 2.2 supersonic flow. The results indicate that, when applying plasma aerodynamic actuation, the start position of the shock wave moves upstream 1 mm to 8 mm averagely, the shock wave angle decreases by 4% to 8% averagely, and the shock wave intensity weakens by 8% to 26% averagely. The local plasma aerodynamic actuation can produce high temperature and pressure plasma layer. The plasma layer makes the separation point of the boundary layer move upstream, which changes the
Based on surface arc plasma aerodynamic actuation, demonstration experiments have been conducted on the variation rules of the shock wave’s position, degree and intensity through varying actuation conditions (such as discharge channel number and spacing, DC discharge voltage, ramp angle and magnetic field) in Mach number 2.2 supersonic flow. The results indicate that, when applying plasma aerodynamic actuation, the start position of the shock wave moves upstream 1 mm to 8 mm averagely, the shock wave angle decreases by 4% to 8% averagely, and the shock wave intensity weakens by 8% to 26% averagely. The local plasma aerodynamic actuation can produce high temperature and pressure plasma layer. The plasma layer makes the separation point of the boundary layer move upstream, which changes the
2010,
22.
Abstract:
In characterizing the fuel layer in ICF cryogenic target by the interferometry, it is inevitable that the target vibrates due to the vibration of the mechanically-cooling and vacuum-pumping system. This leads to different interference patterns of the cryotarget with different states at different times, which is called the interferogram vibration. A method based on the digital-image-processing technology to eliminate this vibration is introduced. By capturing the position and interference images simultaneously by two identical CCDs, the position image is used to determine the vibration degree of targets for processing the interference at a defined state. Four algorithms, frequency estimation, projection demarcation, feature match, and full match are developed to determine the position of th
In characterizing the fuel layer in ICF cryogenic target by the interferometry, it is inevitable that the target vibrates due to the vibration of the mechanically-cooling and vacuum-pumping system. This leads to different interference patterns of the cryotarget with different states at different times, which is called the interferogram vibration. A method based on the digital-image-processing technology to eliminate this vibration is introduced. By capturing the position and interference images simultaneously by two identical CCDs, the position image is used to determine the vibration degree of targets for processing the interference at a defined state. Four algorithms, frequency estimation, projection demarcation, feature match, and full match are developed to determine the position of th
2010,
22.
Abstract:
Operation principle, design principle, fabrication and cautions in operation of ultrahigh pressure He booster system are introduced, and main parts selection method and high pressure seal design of the booster system are discussed. The asdeveloped system can output 300 MPa helium gas with (3.5～5.0)×1010-7 Pa·m3//s leak rate through manual or automatic pressure boosting and keeping. Main function parameters of the system are accessed and compared with those of three congeneric systems. The result shows that the system was rationally designed with superior performance and safety, and the system would be used to test ICF microsphere filling DT system.
Operation principle, design principle, fabrication and cautions in operation of ultrahigh pressure He booster system are introduced, and main parts selection method and high pressure seal design of the booster system are discussed. The asdeveloped system can output 300 MPa helium gas with (3.5～5.0)×1010-7 Pa·m3//s leak rate through manual or automatic pressure boosting and keeping. Main function parameters of the system are accessed and compared with those of three congeneric systems. The result shows that the system was rationally designed with superior performance and safety, and the system would be used to test ICF microsphere filling DT system.
2010,
22.
Abstract:
The Br doped polystyrene film with the sine wave modulated pattern was fabricated and the composite planar target comprising patterned film and foam was also explored by casting the foam solution on the patterned film. Attempts to make composite planar target with sine wave pattern were be discussed and the profile was characterized by the Form Talysurf Series 2 and microscope. The target was intended for Rayleigh-Taylor instabilities.The study indicates that it is easy to controll the film thickness and foam density of the target and to fabricate and assemble the target．
The Br doped polystyrene film with the sine wave modulated pattern was fabricated and the composite planar target comprising patterned film and foam was also explored by casting the foam solution on the patterned film. Attempts to make composite planar target with sine wave pattern were be discussed and the profile was characterized by the Form Talysurf Series 2 and microscope. The target was intended for Rayleigh-Taylor instabilities.The study indicates that it is easy to controll the film thickness and foam density of the target and to fabricate and assemble the target．
2010,
22.
Abstract:
The reason is theoretically discussed for the existence of sub-diffractive spots around the focal spot and the decrease of diffraction efficiency in beam smoothing by 320 mm-diameter diffractive optical elements. Through the simulation analysis, it is suggested that, by means of adjusting the design parameters, the intensity of sub-diffractive spots can be suppressed effectively, which can ensure the effect of diffractive optical elements in beam smoothing. For example, by appropriately increasing sampling points, the proportion of focal spot to whole output range, named Yita, can be decreased, and the efficiency loss engendered by sub-diffractive spots would be restricted. When Yita is less than 0.2, the efficiency loss can be controlled within 2%. The experimental results with 70 mm- and
The reason is theoretically discussed for the existence of sub-diffractive spots around the focal spot and the decrease of diffraction efficiency in beam smoothing by 320 mm-diameter diffractive optical elements. Through the simulation analysis, it is suggested that, by means of adjusting the design parameters, the intensity of sub-diffractive spots can be suppressed effectively, which can ensure the effect of diffractive optical elements in beam smoothing. For example, by appropriately increasing sampling points, the proportion of focal spot to whole output range, named Yita, can be decreased, and the efficiency loss engendered by sub-diffractive spots would be restricted. When Yita is less than 0.2, the efficiency loss can be controlled within 2%. The experimental results with 70 mm- and
2010,
22.
Abstract:
CsI scintillating films with micro-columnar structure were deposited on the silica glass substrates by thermal evaporation. Their morphologies, crystal structures and luminescent properties were analyzed with X-ray diffraction, scanning electron microscope and emission spectrum. The results showed that for substrate temperature of 260℃ and the deposition rate of 3 nm·s-1, the film was deposited would have an ideal micro-columnar morphology, (110) preferred orientation and good transmittance. The CsI film would exhibit two emission peaks at 303 nm and 438 nm under UV excitation, where the later peak was dominant. However, the former peak would shift to 315 nm and became the main one under X-ray excitation, whilst the peak near 438 nm was quite small. The phenomenon indicated th
CsI scintillating films with micro-columnar structure were deposited on the silica glass substrates by thermal evaporation. Their morphologies, crystal structures and luminescent properties were analyzed with X-ray diffraction, scanning electron microscope and emission spectrum. The results showed that for substrate temperature of 260℃ and the deposition rate of 3 nm·s-1, the film was deposited would have an ideal micro-columnar morphology, (110) preferred orientation and good transmittance. The CsI film would exhibit two emission peaks at 303 nm and 438 nm under UV excitation, where the later peak was dominant. However, the former peak would shift to 315 nm and became the main one under X-ray excitation, whilst the peak near 438 nm was quite small. The phenomenon indicated th
2010,
22.
Abstract:
The electroencephalogram (EEG) in rat was measured when the rat was irradiated by high power 35 GHz millimeter wave. By wavelet multi-resolution analysis, the EEG was decomposed into several rhythms to analyze its change. During irradiation, there were nonrhythmic δ waves with high amplitude in EEG and epileptic discharges in slow wave, which suggested that it came about highly disordered rhythm in the EEG and it entered into incapacitating state induced by strong stimulation. The incapacitating period was from (1.3±0.5) s to (17.2±2.3) s. When the irradiation ended at 30 s, the rat EEG began recovering at (62.7±2.6) s. These results demonstrated that the best incapacitating period was when the rat cuticle temperature rose more quickly and its injury was milder during high power mill
The electroencephalogram (EEG) in rat was measured when the rat was irradiated by high power 35 GHz millimeter wave. By wavelet multi-resolution analysis, the EEG was decomposed into several rhythms to analyze its change. During irradiation, there were nonrhythmic δ waves with high amplitude in EEG and epileptic discharges in slow wave, which suggested that it came about highly disordered rhythm in the EEG and it entered into incapacitating state induced by strong stimulation. The incapacitating period was from (1.3±0.5) s to (17.2±2.3) s. When the irradiation ended at 30 s, the rat EEG began recovering at (62.7±2.6) s. These results demonstrated that the best incapacitating period was when the rat cuticle temperature rose more quickly and its injury was milder during high power mill
2010,
22.
Abstract:
The parameters of higher order transverse magnetic modes TMn10 in coaxial cavity in high frequency band are investigated. It is found for given frequency that the cavity cross-section size and the TMn10 order can be freely chosen according to the power and purpose of the device. This implies that, even in high frequency band, large cavity cross-section size can be adopted, which avails to increase power. To widen bandwidth by making the working mode far away from neighboring modes and obtain great characteristic impedance, we can adjust cavity size and select mode according to the mode charts plotted. The calculation shows good agreement with the simulation using the 3D high frequency electromagnetic field software ISFEL.
The parameters of higher order transverse magnetic modes TMn10 in coaxial cavity in high frequency band are investigated. It is found for given frequency that the cavity cross-section size and the TMn10 order can be freely chosen according to the power and purpose of the device. This implies that, even in high frequency band, large cavity cross-section size can be adopted, which avails to increase power. To widen bandwidth by making the working mode far away from neighboring modes and obtain great characteristic impedance, we can adjust cavity size and select mode according to the mode charts plotted. The calculation shows good agreement with the simulation using the 3D high frequency electromagnetic field software ISFEL.
2010,
22.
Abstract:
An S-band relativistic backward wave oscillator without external guiding magnetic field has been investigated using the Karat 2.5D particle-in-cell simulation code. An anode foil is used to extract the electron beam and the non-uniform slow-wave-structure is designed for increasing the microwave output power of the device. Detailed beam-wave interaction pictures in the oscillator were presented. The simulation results show that a 2.79 GHz, 158 MW high power microwave can be obtained when the beam energy is 330 kV and the beam current is about 2.83 kA. The oscillator starts to oscillate at 15 ns, and the nonlinear saturation of the device occurs at about 25 ns. The efficiency is about 16.8% after saturation.
An S-band relativistic backward wave oscillator without external guiding magnetic field has been investigated using the Karat 2.5D particle-in-cell simulation code. An anode foil is used to extract the electron beam and the non-uniform slow-wave-structure is designed for increasing the microwave output power of the device. Detailed beam-wave interaction pictures in the oscillator were presented. The simulation results show that a 2.79 GHz, 158 MW high power microwave can be obtained when the beam energy is 330 kV and the beam current is about 2.83 kA. The oscillator starts to oscillate at 15 ns, and the nonlinear saturation of the device occurs at about 25 ns. The efficiency is about 16.8% after saturation.
2010,
22.
Abstract:
The C-band magnetically insulated transmission line oscillator(MILO) has been simulated by the three dimensional PIC code in order to study the influence of non-symmetry excitation mechanisms on its output modes. It is found that the non-symmetry excitation mechanisms, such as random emitting of cathode electron and the long rise time and low magnitude of input voltage, could produce higher order modes and reduce output power. The 3.6 GHz fundamental mode of the designed MILO, and three higher order eigenmodes of 3.7, 4.1, 4.6 GHz were found in the simulation.The results are similar to those obtained by Karat.
The C-band magnetically insulated transmission line oscillator(MILO) has been simulated by the three dimensional PIC code in order to study the influence of non-symmetry excitation mechanisms on its output modes. It is found that the non-symmetry excitation mechanisms, such as random emitting of cathode electron and the long rise time and low magnitude of input voltage, could produce higher order modes and reduce output power. The 3.6 GHz fundamental mode of the designed MILO, and three higher order eigenmodes of 3.7, 4.1, 4.6 GHz were found in the simulation.The results are similar to those obtained by Karat.
2010,
22.
Abstract:
The theory on beam scan of ultrawide-band (UWB) time-domain antenna is introduced, and it is pointed out that accurate delay between antenna units is the key problem. Therefore, an accurate delay-controller, used in beam scan of UWB time-domain antenna array, has been designed with 50 ps delay step and 10 ps precision. Experiments on beam scan of a 4-unit UWB antenna array with unit spacing of 42 cm has been conducted with this controller controlling the delay between units. The scan step of angle is less than 2°, and the actual scan angles are -0.5°， 10.5°， 20°and 29.5° respectively for the objective angles of 0°， 10°， 20° and 30°. The error between experimental result and theoretical caculation is under 1°.
The theory on beam scan of ultrawide-band (UWB) time-domain antenna is introduced, and it is pointed out that accurate delay between antenna units is the key problem. Therefore, an accurate delay-controller, used in beam scan of UWB time-domain antenna array, has been designed with 50 ps delay step and 10 ps precision. Experiments on beam scan of a 4-unit UWB antenna array with unit spacing of 42 cm has been conducted with this controller controlling the delay between units. The scan step of angle is less than 2°, and the actual scan angles are -0.5°， 10.5°， 20°and 29.5° respectively for the objective angles of 0°， 10°， 20° and 30°. The error between experimental result and theoretical caculation is under 1°.
2010,
22.
Abstract:
The motion and energy of electron in linearly polarized laser standing wave field are calculated with the relativistic Lorentz equation. The results show that there is a critical electron energy, and the balancing position of electron oscillation changes from nodes to antinodes at the incident electron energy in excess of the critical energy. At the incidence of antinode plane parallel to the electric field, the high energy electron is driven by the strong electric filed and the velocity and energy of the electron has a fast oscillation with the amplitude envelope as a cosine structure. The electron, however, is driven by the Lorentz field at the incidence of the node plane vertical to the magnetic field. The electron oscillates, gaining and losing energy in front and behind the standing w
The motion and energy of electron in linearly polarized laser standing wave field are calculated with the relativistic Lorentz equation. The results show that there is a critical electron energy, and the balancing position of electron oscillation changes from nodes to antinodes at the incident electron energy in excess of the critical energy. At the incidence of antinode plane parallel to the electric field, the high energy electron is driven by the strong electric filed and the velocity and energy of the electron has a fast oscillation with the amplitude envelope as a cosine structure. The electron, however, is driven by the Lorentz field at the incidence of the node plane vertical to the magnetic field. The electron oscillates, gaining and losing energy in front and behind the standing w
2010,
22.
Abstract:
In order to restore damaged radiography images, a new image inpainting algorithm for radiography has been proposed based on partial differential equations. This algorithm adopts p-Laplace operator of variational parameter into the curvature driven diffusions(CDD) model, and restores the damaged image using the improved model and the BSCB model by turns. By using the information along both tangent directions and gradient directions, the proposed algorithm can meet the connectivity principle of human vision perception and restore large damaged domain satisfactorily. It is proved that the new algorithm has better performance in convergence speed and inpainting quality compared with CDD model.
In order to restore damaged radiography images, a new image inpainting algorithm for radiography has been proposed based on partial differential equations. This algorithm adopts p-Laplace operator of variational parameter into the curvature driven diffusions(CDD) model, and restores the damaged image using the improved model and the BSCB model by turns. By using the information along both tangent directions and gradient directions, the proposed algorithm can meet the connectivity principle of human vision perception and restore large damaged domain satisfactorily. It is proved that the new algorithm has better performance in convergence speed and inpainting quality compared with CDD model.
2010,
22.
Abstract:
Extreme ultraviolet lithography(EUVL) is regarded as one of the most promising next generation lithographies. Among all the EUVL system technologies, the extreme ultraviolet source is the key issue. Compared with other light sources, gas discharge-produced plasma extreme ultraviolet source has drawn much attention around the world for its advantages in many aspects.The main pulse power generator for the Z-pinch discharge produced plasma extreme ultraviolet source is decribed in this paper, the circuit topology is presented. The critical 3-stage magnetic pulse compression is emphasized, its parameters are presented in the paper. Moreover, a novel configuration of the final magnetic pulse conpression unit is introduced. Experiment results show that each pulse compression effect meets the ant
Extreme ultraviolet lithography(EUVL) is regarded as one of the most promising next generation lithographies. Among all the EUVL system technologies, the extreme ultraviolet source is the key issue. Compared with other light sources, gas discharge-produced plasma extreme ultraviolet source has drawn much attention around the world for its advantages in many aspects.The main pulse power generator for the Z-pinch discharge produced plasma extreme ultraviolet source is decribed in this paper, the circuit topology is presented. The critical 3-stage magnetic pulse compression is emphasized, its parameters are presented in the paper. Moreover, a novel configuration of the final magnetic pulse conpression unit is introduced. Experiment results show that each pulse compression effect meets the ant
2010,
22.
Abstract:
The surface spike microstructures are formed by Nd:YAG nanosecond laser pulses irradiating single crystal silicon wafers with energy densities within the ablation regime, in SF6 or air atmosphere. All the tops of the spikes created in SF6 atmosphere have small spheres, there are still the secondary tips on some spikes. There is granular material on the top and the edge of the spikes induced by nanosecond laser pulses in air atmosphere, which is formed by solidification of the droplets. The microstructures formed in air are different from the slender whiskerlike structures created by excimer laser and also different from the conical microstructures with dendritic nanostructures formed under femtosecond laser irradiation. The experimental results suggest that both the l
The surface spike microstructures are formed by Nd:YAG nanosecond laser pulses irradiating single crystal silicon wafers with energy densities within the ablation regime, in SF6 or air atmosphere. All the tops of the spikes created in SF6 atmosphere have small spheres, there are still the secondary tips on some spikes. There is granular material on the top and the edge of the spikes induced by nanosecond laser pulses in air atmosphere, which is formed by solidification of the droplets. The microstructures formed in air are different from the slender whiskerlike structures created by excimer laser and also different from the conical microstructures with dendritic nanostructures formed under femtosecond laser irradiation. The experimental results suggest that both the l
2010,
22.
Abstract:
Carbon nanotube was deposited on Si substrate which was intentionally covered with a certain thickness SiO2 layer as the interface barrier. A doublepotential barrier model was proposed and the tunneling probability of the two barriers in the external electric field was qualitatively discussed. The two variable tunneling probabilities of interface barrier and surface barrier are the reason of the nonlinearity of the Fowler-Nordheim(F-N) plots. The plots follow the F-N law in low electric field because the tunneling probability of interface barrier is larger than that of surface barrier. The plots do not follow the F-N law in high electric field because the tunneling probability of surface barrier is higher．
Carbon nanotube was deposited on Si substrate which was intentionally covered with a certain thickness SiO2 layer as the interface barrier. A doublepotential barrier model was proposed and the tunneling probability of the two barriers in the external electric field was qualitatively discussed. The two variable tunneling probabilities of interface barrier and surface barrier are the reason of the nonlinearity of the Fowler-Nordheim(F-N) plots. The plots follow the F-N law in low electric field because the tunneling probability of interface barrier is larger than that of surface barrier. The plots do not follow the F-N law in high electric field because the tunneling probability of surface barrier is higher．
2010,
22.
Abstract:
With particle-in-cell and Monte Carlo collision method, a two dimensional axisymmetric model is established to study the ion thruster plume characteristics. The simulated results are compared with experimental data, which shows good agreement and suggests that, the model can evaluate the characteristics of ion thruster plume very well. The ion number density can reach 1014 m-3 in the backflow region, which can cause erosion of the spacecraft; the back pressure’s visible influence on the charge exchange ions outside the beam region can not be neglected.
With particle-in-cell and Monte Carlo collision method, a two dimensional axisymmetric model is established to study the ion thruster plume characteristics. The simulated results are compared with experimental data, which shows good agreement and suggests that, the model can evaluate the characteristics of ion thruster plume very well. The ion number density can reach 1014 m-3 in the backflow region, which can cause erosion of the spacecraft; the back pressure’s visible influence on the charge exchange ions outside the beam region can not be neglected.
2010,
22.
Abstract:
In a CCD based neutron radiography system, some fluorescent light will be reflected back to the scintillator by the mirror if the mirror is too close to the scintillator. Some of the incoming neutrons may also be scattered back to the scintillator. These two factors form a strong background that cannot be neglected. This background is harmful to quantitative analysis and CT reconstruction. The analytic calculation of the reflection component as the well as Monte Carlo simulation of the back-scattering component has been carried out, the result of which agrees well with the background measurements. The background component introduced by mirror accounts for more than 10% of the whole background in a typical detection system configuration.
In a CCD based neutron radiography system, some fluorescent light will be reflected back to the scintillator by the mirror if the mirror is too close to the scintillator. Some of the incoming neutrons may also be scattered back to the scintillator. These two factors form a strong background that cannot be neglected. This background is harmful to quantitative analysis and CT reconstruction. The analytic calculation of the reflection component as the well as Monte Carlo simulation of the back-scattering component has been carried out, the result of which agrees well with the background measurements. The background component introduced by mirror accounts for more than 10% of the whole background in a typical detection system configuration.
2010,
22.
Abstract:
The initial discharge process of pseudospark switch has been simulated via a electrostatic particle-in-cell plus Monte-Carlo collision method. The pseudospark discharge process mainly consists of Townsend process, plasma formation, hollow cathode effect and main discharge induced by field emission. The plasma formation and hollow cathode effect are critical for the conduction. Then the parameters, i.e. gas pressure, electrode borehole diameter, anode voltage and initial particle density, were varied and their effect on the forming time of electron peak current of the pseudospark switch was investigated. The results show that as the parameters increase, the forming time of electron peak current lessens.
The initial discharge process of pseudospark switch has been simulated via a electrostatic particle-in-cell plus Monte-Carlo collision method. The pseudospark discharge process mainly consists of Townsend process, plasma formation, hollow cathode effect and main discharge induced by field emission. The plasma formation and hollow cathode effect are critical for the conduction. Then the parameters, i.e. gas pressure, electrode borehole diameter, anode voltage and initial particle density, were varied and their effect on the forming time of electron peak current of the pseudospark switch was investigated. The results show that as the parameters increase, the forming time of electron peak current lessens.
2010,
22.
Abstract:
The difference of photocurrent waveforms from the semi-insulating GaAs photoconductive semiconductor switch(PCSS) when using different exterior electric parameters has been investigated. According to the results the influence of exterior electric parameters has been discussed. The test switch was fabricated of 600 μm thick semi-insulating GaAs and the gap was 12 mm. The PCSS was illuminated by laser pulse with incident optical energy of 5.2 mJ at wavelength of 1 064 nm and the photocurrent waveforms were recorded by current probe. The test results show the influence of trigger light, curcuit inductance and storage capacitor on the photocurrent waveform. The rise time is affected by the inductance of the circuit. The capacitor plays a decisive role in the maintaining of the nonlinear mode
The difference of photocurrent waveforms from the semi-insulating GaAs photoconductive semiconductor switch(PCSS) when using different exterior electric parameters has been investigated. According to the results the influence of exterior electric parameters has been discussed. The test switch was fabricated of 600 μm thick semi-insulating GaAs and the gap was 12 mm. The PCSS was illuminated by laser pulse with incident optical energy of 5.2 mJ at wavelength of 1 064 nm and the photocurrent waveforms were recorded by current probe. The test results show the influence of trigger light, curcuit inductance and storage capacitor on the photocurrent waveform. The rise time is affected by the inductance of the circuit. The capacitor plays a decisive role in the maintaining of the nonlinear mode
2010,
22.
Abstract:
The broadband transmission-line transformer with 4∶1 impedance transformation ratio is studied, its equivalent model with mutual coupling between transmission-lines is given, and its impedance transformation characteristics are analyzed. Then the permeability change with frequency neglected in conventional equivalent model is taken into account, and the property of the NiZn broadband transmission-line transformer is analyzed as an example. Result comparison between experiment and equivalent model analyses shows that the permeability change with frequency does have effect on analysis results, thus should be considered．
The broadband transmission-line transformer with 4∶1 impedance transformation ratio is studied, its equivalent model with mutual coupling between transmission-lines is given, and its impedance transformation characteristics are analyzed. Then the permeability change with frequency neglected in conventional equivalent model is taken into account, and the property of the NiZn broadband transmission-line transformer is analyzed as an example. Result comparison between experiment and equivalent model analyses shows that the permeability change with frequency does have effect on analysis results, thus should be considered．
2010,
22.
Abstract:
Based on the particle-in-cell(PIC) simulation, a new method is proposed to compute the equivalent inductance and capacitance of magnetically insulated transmission line(MITL). Two scaling factors are introduced into the expressions for the equivalent inductance and capacitance of the coaxial MITL, which are derived from the laminar flow model. The voltage-ependent expressions of the two factors are obtained by fitting the PIC simulation results. The rescaled equivalent capacitance and inductance can match the PIC simulation results well, thus the results obtained can be used for the circuit modeling of MITLs．
Based on the particle-in-cell(PIC) simulation, a new method is proposed to compute the equivalent inductance and capacitance of magnetically insulated transmission line(MITL). Two scaling factors are introduced into the expressions for the equivalent inductance and capacitance of the coaxial MITL, which are derived from the laminar flow model. The voltage-ependent expressions of the two factors are obtained by fitting the PIC simulation results. The rescaled equivalent capacitance and inductance can match the PIC simulation results well, thus the results obtained can be used for the circuit modeling of MITLs．
2010,
22.
Abstract:
Due to its advantages at low frequency, a 4-rod radiofrequency quadrupole(RFQ) structure has been adopted for the RFQ cavity at the Institute of Modern Physics, Chinese Academy of Sciences, which works at 100 MHz and is used for the direct plasma injection scheme. After the beam dynamics design, the parameters of the stems of the cavity were optimized to obtain the maximum shunt impedance. The capacitance existing in the projecting electrodes will affect the properties of the cavity, therefore, the influence of the projecting electrodes should be taken into account. Their influence on shunt impedance and flatness of the 4-rod RFQ cavity was studied, and the results show that the influence on shunt impedance can be neglected but it can not be neglected on flatness. In addition, the length r
Due to its advantages at low frequency, a 4-rod radiofrequency quadrupole(RFQ) structure has been adopted for the RFQ cavity at the Institute of Modern Physics, Chinese Academy of Sciences, which works at 100 MHz and is used for the direct plasma injection scheme. After the beam dynamics design, the parameters of the stems of the cavity were optimized to obtain the maximum shunt impedance. The capacitance existing in the projecting electrodes will affect the properties of the cavity, therefore, the influence of the projecting electrodes should be taken into account. Their influence on shunt impedance and flatness of the 4-rod RFQ cavity was studied, and the results show that the influence on shunt impedance can be neglected but it can not be neglected on flatness. In addition, the length r
2010,
22.
Abstract:
A step motor for frequency tuning was installed inside the separated function radio frequency quadruple(SFRFQ) accelerator. The operating frequency of the SFRFQ cavity can therefore be precisely tuned at 26.07 MHz either manually or by computer algorithm, and then the resonant frequency match can be achieved between SFRFQ and RFQ cavities in our combined accelerator system. Also the roentgen spectrum in the high power test of the SFRFQ cavity shows that the inter-vane voltage reaches 86.2 kV, exceeding the design value 70 kV, when the input signal has 1/6 duty cycle and 28.8 kW peak power.
A step motor for frequency tuning was installed inside the separated function radio frequency quadruple(SFRFQ) accelerator. The operating frequency of the SFRFQ cavity can therefore be precisely tuned at 26.07 MHz either manually or by computer algorithm, and then the resonant frequency match can be achieved between SFRFQ and RFQ cavities in our combined accelerator system. Also the roentgen spectrum in the high power test of the SFRFQ cavity shows that the inter-vane voltage reaches 86.2 kV, exceeding the design value 70 kV, when the input signal has 1/6 duty cycle and 28.8 kW peak power.
2010,
22.
Abstract:
Scatter is an important problem in high-energy flash X-ray radiography. The X-ray transport of flash radiograph about FTO (French test object) was simulated by means of Monte-Carlo method to investigate the influences and the main source of side scatter. The results show that without side cone, the front cone is the main source of side scatter in the system. For any pixel, the scattered exposure from the front cone is more than 50% of the total exposure. And the side scatter has a monotony distribution in the axis direction. With side cone the side scattered exposure is decreased, and the distribution becomes complicated with single-peak in the direction perpendicular to the axis. In addition, the increment of the distance between the recording plane and the center of the target may not le
Scatter is an important problem in high-energy flash X-ray radiography. The X-ray transport of flash radiograph about FTO (French test object) was simulated by means of Monte-Carlo method to investigate the influences and the main source of side scatter. The results show that without side cone, the front cone is the main source of side scatter in the system. For any pixel, the scattered exposure from the front cone is more than 50% of the total exposure. And the side scatter has a monotony distribution in the axis direction. With side cone the side scattered exposure is decreased, and the distribution becomes complicated with single-peak in the direction perpendicular to the axis. In addition, the increment of the distance between the recording plane and the center of the target may not le
2010,
22.
Abstract:
The Dragon-Ⅰlinear induction accelerator(LIA) uses mm level diameter pulsed electron beam to strike the bremsstrahlung converter target to generate X-ray, which generates the backstreaming ions as well. Four Faraday cups are combined to collect backstreaming ions produced at the bremsstrahlung converter target of the Dragon-ⅠLIA. Experiment and calculation results show that the backstreaming positive ions density and velocity are about 1021/m3 and 2～3 km/s,respectively.The calculated results show that the intensity of the backstreaming positive ion beam is only 0.27% of that of the targeting electron beam, thus the backstreaming ions would not affect the focus of the electron beam.
The Dragon-Ⅰlinear induction accelerator(LIA) uses mm level diameter pulsed electron beam to strike the bremsstrahlung converter target to generate X-ray, which generates the backstreaming ions as well. Four Faraday cups are combined to collect backstreaming ions produced at the bremsstrahlung converter target of the Dragon-ⅠLIA. Experiment and calculation results show that the backstreaming positive ions density and velocity are about 1021/m3 and 2～3 km/s,respectively.The calculated results show that the intensity of the backstreaming positive ion beam is only 0.27% of that of the targeting electron beam, thus the backstreaming ions would not affect the focus of the electron beam.
2010,
22.
Abstract:
Pulsed discharge in water produces transient shockwaves which are harmful to the ceramic interface in accelerators. In this paper, with a self-consistent underwater explosive approach, a finite element model was set up to investigate the shockwave behaviors, and the pressure-time history and ceramic mechanical response to shockwaves were presented. In order to get the pressure profile and verify the calculation models, a small-scaled water switch test was conducted based on a 10-stage Marx generator (40~50 ns pulse duration, 100~300 kV amplitude). The variations of peak pressure, shock velocity and main pulse width under different breakdown conditions were measured. According to the calculation of empirical formulas, about 17% of the discharge energy was transformed into the mechanical ene
Pulsed discharge in water produces transient shockwaves which are harmful to the ceramic interface in accelerators. In this paper, with a self-consistent underwater explosive approach, a finite element model was set up to investigate the shockwave behaviors, and the pressure-time history and ceramic mechanical response to shockwaves were presented. In order to get the pressure profile and verify the calculation models, a small-scaled water switch test was conducted based on a 10-stage Marx generator (40~50 ns pulse duration, 100~300 kV amplitude). The variations of peak pressure, shock velocity and main pulse width under different breakdown conditions were measured. According to the calculation of empirical formulas, about 17% of the discharge energy was transformed into the mechanical ene
2010,
22.
Abstract:
The resonant frequency of the high intensity proton RFQ accelerator at the Institute of High Energy Physics is 352.2 MHz, and the control precision of the accelerating field is ±1% in amplitude and ±1° in phase, respectively. In order to accomplish these requirements, a digital low-level RF(LLRF) control system is adopted. This system includes three parts: the accelerating field amplitude and phase control, the cavity resonant frequency control and the high power interlock protection. The down-conversion of the cavity sampling signal and the up-conversion of the feedback excitation signal are realized by the analog devices. The real time feedback control of amplitude and phase adopts digital I/Q demodulation, and is assembled in a FPGA block, where three DSP blocks are used for communic
The resonant frequency of the high intensity proton RFQ accelerator at the Institute of High Energy Physics is 352.2 MHz, and the control precision of the accelerating field is ±1% in amplitude and ±1° in phase, respectively. In order to accomplish these requirements, a digital low-level RF(LLRF) control system is adopted. This system includes three parts: the accelerating field amplitude and phase control, the cavity resonant frequency control and the high power interlock protection. The down-conversion of the cavity sampling signal and the up-conversion of the feedback excitation signal are realized by the analog devices. The real time feedback control of amplitude and phase adopts digital I/Q demodulation, and is assembled in a FPGA block, where three DSP blocks are used for communic
